The transition to the ANZ DC-10 was in May 1975. I was a regular on these at the time. Prior to that BOAC (still until April 1974) and finally BA had since 1972 operated a 707, ostensibly nonstop but the westbound made an unannounced stop in Winnipeg. Prior to that, it was a VC-10 through JFK and continuing to Sydney.
BOAC at that time also operated quite a number of transatlantic charters, with 707s, trading separately as "BOAC Ltd" to appease IATA, and LAX was one of the more common destinations. These used a small pool of economy-only 707s, which also were used on scheduled services to Toronto, although strangely nowhere else.